Publications by authors named "Apinya Assavanig"

8 Publications

  • Page 1 of 1

Development and characterization of bio-derived polyhydroxyalkanoate nanoparticles as a delivery system for hydrophobic photodynamic therapy agents.

J Mater Sci Mater Med 2016 Feb 28;27(2):40. Epub 2015 Dec 28.

Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand.

In this study, we developed and investigated nanoparticles of biologically-derived, biodegradable polyhydroxyalkanoates (PHAs) as carriers of a hydrophobic photosensitizer, 5,10,15,20-Tetrakis(4-hydroxy-phenyl)-21H, 23H-porphine (pTHPP) for photodynamic therapy (PDT). Three PHA variants; polyhydroxybutyrate, poly(hydroxybutyrate-co-hydroxyvalerate) or P(HB-HV) with 12 and 50% HV were used to formulate pTHPP-loaded PHA nanoparticles by an emulsification-diffusion method, where we compared two different poly(vinyl alcohol) (PVA) stabilizers. The nanoparticles exhibited nano-scale spherical morphology under TEM and hydrodynamic diameters ranging from 169.0 to 211.2 nm with narrow size distribution. The amount of drug loaded and the drug entrapment efficiency were also investigated. The in vitro photocytotoxicity was evaluated using human colon adenocarcinoma cell line HT-29 and revealed time and concentration dependent cell death, consistent with a gradual release pattern of pTHPP over 24 h. This study is the first demonstration using bacterially derived P(HB-HV) copolymers for nanoparticle delivery of a hydrophobic photosensitizer drug and their potential application in PDT.
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http://dx.doi.org/10.1007/s10856-015-5655-4DOI Listing
February 2016

Glutaminase-producing Meyerozyma (Pichia) guilliermondii isolated from Thai soy sauce fermentation.

Int J Food Microbiol 2015 Jan 22;192:7-12. Epub 2014 Sep 22.

Department of Biotechnology, Faculty of Science, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand. Electronic address:

In this study, 34 yeast isolates were obtained from koji and moromi samples of Thai soy sauce fermentation. However, the most interesting yeast strain was isolated from the enriched 2 month-old (M2) moromi sample and identified as Meyerozyma (Pichia) guilliermondii EM2Y61. This strain is a salt-tolerant yeast that could tolerate up to 20% (w/v) NaCl and produce extracellular and cell-bound glutaminases. Interestingly, its glutaminases were more active in 18% (w/v) NaCl which is a salt concentration in moromi. The extracellular glutaminase's activity was found to be much higher than that of cell-bound glutaminase. The highest specific activity and stability of the extracellular glutaminase were found in 18% (w/v) NaCl at pH4.5 and 37°C. A challenge test by adding partially-purified extracellular glutaminase from M. guilliermondii EM2Y61 into 1 month-old (M1) moromi sample showed an increased conversion of L-glutamine to L-glutamic acid. This is the first report of glutaminase producing M. guilliermondii isolated from the moromi of Thai soy sauce fermentation. The results suggested the potential application of M. guilliermondii EM2Y61 as starter yeast culture to increase l-glutamic acid during soy sauce fermentation.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2014.09.019DOI Listing
January 2015

Co-culturing of Pichia guilliermondii enhanced volatile flavor compound formation by Zygosaccharomyces rouxii in the model system of Thai soy sauce fermentation.

Int J Food Microbiol 2013 Jan 16;160(3):282-9. Epub 2012 Nov 16.

Department of Biotechnology, Faculty of Science, Mahidol University, Rama VI Rd., Bangkok, Thailand.

The roles of salt-tolerant yeasts such as Zygosaccharomyces rouxii, Candida versatilis, and Candida etchellsii in the production of volatile flavor compounds (VFCs) in soy sauce fermentation have been well documented. However, the knowledge of VFC production by other salt-tolerant yeasts is still limited. In this work, the roles of Z. rouxii and Pichia guilliermondii strains in VFC production were investigated in moromi medium as a model system for soy sauce fermentation. Inoculation of a single culture of either Z. rouxii or P. guilliermondii as well as co-cultures of these two yeasts into moromi medium showed increased numbers of viable yeast at around 0.7 to 1.9 log CFU/mL after 7days of cultivation at 30°C. During cultivation, both single and co-cultures displayed survival over a 7-day time period, compared with the controls (no culture added). Overall, yeast inoculation enhanced the production of VFCs in the moromi media with higher amounts of ethanol, alcohols, furanones, esters, aldehyde, acid, pyrone and phenols, known as important characteristic flavor compounds in soy sauce. Moreover, the co-culture produced more alcohols, furanones, esters, maltol and benzoic acid than the single culture of Z. rouxii.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2012.10.022DOI Listing
January 2013

Isolation and characterization of acid-sensitive Lactobacillus plantarum with application as starter culture for Nham production.

Food Microbiol 2010 Sep 30;27(6):741-8. Epub 2010 Mar 30.

Department of Biotechnology, Faculty of Science, Mahidol University, Rama 6 Road, Bangkok 10400, Thailand.

The aim of this study was to derive new starter culture variants that are unable to grow below pH 4.6, the desirable pH of the Thai fermented pork sausage, Nham, specified by Thailand Food Standard, and apply them in Nham fermentation. Several acid-sensitive mutants of one of the commercial Nham starter cultures, Lactobacillus plantarum BCC 9546, were isolated as spontaneous neomycin-resistant mutants. The growth of three representative mutants was characterized in MRS broth, which revealed that their cell numbers and acid production were lower than that of the wild-type. The H(+)-ATPase activities of the three mutants were found significantly lower than that of the wild-type under either neutral or acidic conditions. Consequently, internal pH values of the mutants appeared to be lower, especially in acidic environment (pH 5). The most acid-sensitive mutant was applied in experimental Nham production and the pH of Nham fermented with the mutant had significantly higher pH at the end of fermentation (3 days) and after an additional 4 days of storage at 30 degrees C. These results indicate that the use of acid-sensitive L. plantarum as starter culture can reduce the severity of post-acidification and increase the shelf life of Nham at ambient temperature.
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http://dx.doi.org/10.1016/j.fm.2010.03.014DOI Listing
September 2010

Broad distribution of enterotoxin genes (hblCDA, nheABC, cytK, and entFM) among Bacillus thuringiensis and Bacillus cereus as shown by novel primers.

Int J Food Microbiol 2008 Feb 17;121(3):352-6. Epub 2007 Nov 17.

Department of Biotechnology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok, 10400, Thailand.

Eight new pairs of PCR primers were designed and efficiently detect eight toxin genes (hblC, hblD, hblA, nheA, nheB, nheC, cytK, and entFM) in 411 B. cereus strains (121 food- and 290 soil isolates) and 205 B. thuringiensis strains (43 serovars, 10 food- and 152 soil isolates). According to the presence of these eight toxin genes, they were divided into four groups among the total 616 isolates. In Group I, all eight genes occurred simultaneously in 403 (65.42%) isolates, while Group II (134 isolates or 21.75%) and Group III (46 isolates or 7.47%) were devoid of hblCDA and cytK, respectively. In Group IV, there were thirty-three isolates which lacked both hblCDA and cytK. The presence of hblCDA in B. thuringiensis strains (86.80%) was significantly higher (P<0.05) than in B. cereus strains (66.18%) whereas no significant difference in nheABC, cytK and entFM occurrence was detected between both bacterial groups. Both nheABC and entFM genes were found in all B. cereus and B. thuringiensis strains (616 strains in total), while the cytK gene could be detected in 365 (88.80%) of the B. cereus and 172 (83.90%) of the B. thuringiensis strains. None of the 616 tested strains showed the presence of only a single or two genes in either the hbl or nhe operons. The eight primer pairs designed for this multiplex PCR allowed rapid detection of eight toxin genes from boiled cells with high sensitivity, gave 100% reproducibility, and did not cross-react to 32 other bacterial strains.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2007.11.013DOI Listing
February 2008

Development and assessment of a real-time pcr assay for rapid and sensitive detection of a novel thermotolerant bacterium, Lactobacillus thermotolerans, in chicken feces.

Appl Environ Microbiol 2005 Aug;71(8):4214-9

Laboratory of Microbial Resources and Ecology, Graduate School of Agriculture, Hokkaido University, Kita-9 Nishi-9, Kita-ku, Sapporo 060-8589, Japan.

A new real-time PCR assay was successfully developed using a TaqMan fluorescence probe for specific detection and enumeration of a novel bacterium, Lactobacillus thermotolerans, in chicken feces. The specific primers and probe were designed based on the L. thermotolerans 16S rRNA gene sequences, and these sequences were compared to those of all available 16S rRNA genes in the GenBank database. The assay, targeting 16S rRNA gene, was evaluated using DNA from a pure culture of L. thermotolerans, DNA from the closely related bacteria Lactobacillus mucosae DSM 13345(T) and Lactobacillus fermentum JCM 1173(T), and DNA from other lactic acid bacteria in quantitative experiments. Serial dilutions of L. thermotolerans DNA were used as external standards for calibration. The minimum detection limit of this technique was 1.84 x 10(3) cells/ml of an L. thermotolerans pure culture. The assay was then applied to chicken feces in two different trials. In the first trial, the cell population was 10(4) cells/g feces on day 4 and 10(5) cells/g feces on days 11 to 18. However, cell populations of 10(6) to 10(7) cells/g feces were detected in the second trial. The total bacterial count, measured by 4',6-diamidino-2-phenylindole (DAPI) staining, was approximately 10(11) cells/g feces. These results suggest that in general, L. thermotolerans is a normal member of the chicken gut microbiota, although it is present at relatively low levels in the feces.
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http://dx.doi.org/10.1128/AEM.71.8.4214-4219.2005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1183300PMC
August 2005

Influence of minced pork and rind ratios on physico-chemical and sensory quality of Nham - a Thai fermented pork sausage.

Meat Sci 2005 Feb;69(2):355-62

National Center for Genetic Engineering and Biotechnology, 113 Paholyothin Rd., Klong 1, Klong Luang, Pathumthani 12120, Thailand.

The effects of incorporating varying levels of minced pork and rind on physico-chemical and sensory quality of Nham were studied. An increase in cooked pork rind resulted in higher moisture, lipid, and initial pH values of Nham (P<0.05). However, no significant effects were observed on fermentation characteristics of Nham (P>0.05). At the end of fermentation, Nham with a higher meat component exhibited higher texture profile analysis force, hardness, and cohesiveness (P<0.05). The results suggested the importance of meat on the restructuring effect, which contributes to the texture formation of Nham. Incorporation of a higher amount of cooked pork rind improved water-binding properties, leading to decreased weight loss and released water. Based on the results of sensory evaluation, up to 43% pork rind can be used in the formulation with no adverse effect on texture and overall liking of Nham. However, the ratio of 5:5 was the most appropriate for minimising the cost of production.
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http://dx.doi.org/10.1016/j.meatsci.2004.08.006DOI Listing
February 2005

Lactobacillus thermotolerans sp. nov., a novel thermotolerant species isolated from chicken faeces.

Int J Syst Evol Microbiol 2003 Jan;53(Pt 1):263-268

Laboratory of Microbial Resources and Ecology, Graduate School of Agriculture, Hokkaido University, Kita-9 Nishi-9, Kita-ku, Sapporo 060-8589, Japan.

Five strains of thermotolerant lactic acid bacteria (G 12, G 22, G 35T, G 43 and G 44) isolated from chicken faeces were characterized taxonomically. The strains were facultatively anaerobic, Gram-positive, catalase-negative, non-motile, non-spore-forming rods. They were heterofermentative lactobacilli that produced DL-lactic acid. Growth of the strains occurred at 45 degrees C but not at 15 degrees C. The optimum temperature for growth was 42 degrees C, as determined from the specific growth rate. The highest permissive temperatures for growth were 50 degrees C for strain G35T and 48 degrees C for the other four strains. DNA G+C content of the strains was between 49 and 51 mol%. Complex fatty acid patterns of the strains showed the presence of C14:0, C16:0, sometimes C18:0, C18:1 and C19:0 cyclo in the cell walls. Phylogenetic analysis of the 16S rRNA gene sequences of the five strains placed them in the Lactobacillus caseil Pediococcus group, with Lactobacillus fermentum as their closest relative (about 95% sequence similarity). DNA-DNA hybridization data indicated that the thermotolerant strains were not L. fermentum. Taken together, the findings of this study show that the five strains isolated from chicken faeces represent a novel species within the genus Lactobacillus, for which the name Lactobacillus thermotolerans is proposed (G 35T = DSM 14792T =JCM 11425T).
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http://dx.doi.org/10.1099/ijs.0.02347-0DOI Listing
January 2003